Method for control of texture of dehydrated potatoes



METHOD FOR CONTROL OF TEXTURE OF DEHYDRATED POTATOES James Cording, Jr.,Philadelphia, and Miles I. Willard, Jr., Glenside, Pa., assignors to theUnited States of America as represented by the Secretary of AgricultureNo Drawing. Application May 9, 1955, Serial No. 507,187

1 Claim. (Cl. 99-207) (Granted under Title 35, U. S. Code (1952), sec.266) A nonexclusive, irrevocable, royalty-free license in the inventionherein described, for all governmental purposes, throughout the world,with power to grant sublicenses for such purposes, is hereby granted tothe Government of the United States of America.

This invention relates to processes for the production of dehydratedcooked potatoes and has among its objects the production of dehydratedpotatoes that upon reconstitution yield potatoes having substantiallythe appearance, flavor and, in particular, the mealy texture of freshcooked potatoes.

In previously known methods for dehydrating potatoes more or less celldamage occurs so that the products, upon reconstitution, were always ofpoorer texture than the fresh potato. Heretofore, the only known way toproduce dehydrated potatoes that would have the desired mealy textureafter reconstitution has comprised using high solids potatoes as rawmaterial and if the potatoes had been stored at low temperature for anyappreciable time, reconditioning them by storing for about two weeks atordinary temperatures before use. Because of these limitations, a greatpart of the annual potato crop could not be used in the preparation ofdehydrated potato, thus adding to the cost of the dehydrated product andreducing the value of the unsuitable potatoes.

We have now discovered a simple and inexpensive process whereby anysound potatoes, regardless of variety, geographical origin, storagehistory or density, can be converted into dehydrated cooked potatoes ofhigh quality which upon reconstitution by the addition of fluid such aswater or milk yield potatoes having appearance, flavor and texture atleast as good if not better than the same product prepared from thefresh potatoes.

According to the invention, potatoes to be dehydrated are subjected to aprecooking treatment at about 140-1 80 F. for about to 60 minutes, afterwhich they are cooked at about 212 F. for about 16 minutes, mashed, andthen dehydrated by a process as specified below.

The mealiness of the product (after reconstitution) can be accuratelycontrolled by suitable choice of the temperature and time of theprecooking treatment. Naturally, the particular temperature and timerequired to achieve a given degree of mealiness will depend to a largeextent on the type and history of the particular batch of potatoes beingprocessed. In general, maximum mealiness is achieved by precooking at atemperature in the lower part of the range, say about 140-150 F., andfor a fairly long time, say about one hour. Such a treatment, however,may produce an undesirably high degree of mealiness when used on highquality, high solids potatoes, in which case a higher temperature or ashorter time, or both, may be preferable.

Any convenient means of heating the potatoes may be used in theprecooking treatment. A water bath is usually the most practicalalthough steam or hot air may be used. Whole unpeeled potatoes may beused, but as a means of facilitating the transfer of heat into theinterior nitcd States Patent of the potato we generally prefer to cutthe potatoes into slices, cubes or other convenient pieces. In theproduction of dehydrated diced potatoes it may be convenient to dice theraw' potato before the precooking process. For the preparation of flakesor granules the raw potatoes may be cut into any shape or even leftwhole, for the precooking and cooking steps. They are then mashed beforebeing dried.

A product of highest quality is obtained when potato flakes are made bydehydrating the mashed potatoes in the manner described in our copendingapplication entitled, Dehydration of Cooked Potato, filed April 1, 1954,Serial No. 420,475. The process there described comprises drying cookedmashed potato in the form of a thin film (about 0.005 to 0.015 inchthick) on a heated surface to a final moisture content of about 4 to10%. The preferred process utilizes a double drum drier having the rollsheated internally by steam and being adjusted to a clearance of about0.005 to 0.015 inch. The flakes thus produced are of substantiallymonocellular thickness and contain a minimum of ruptured cells and freestarch.

In processing high solids potatoes to'make flakes by our drum dryingmethod it is preferred that the cooked, mashed potatoes be diluted withwater to a solids content of about 20% before dehydration, as is morefully disclosed in our copending application entitled Drum Drying ofCooked Mashed Potatoes, filed November 15, 1954, Serial No. 469,065.Such dilution before drum drying causes the mashed potato to spread onand adhere more uniformly to the rolls of the drier and yields a denserand less fragile flake. Potatoes precooked according to the presentinvention show the same benefits from dilution of the cooked mashedpotatoes before dehydration.

When dehydrated potato flakes or granules made by conventionalprocessesare reconstituted to make mashed potatoes, 1 part by weight ofdehydrated potatoes requires 4 /2 parts of water or water and milk toproduce the normal consistency of mashed potatoes. When dehydratedflakes or granules made by the process of the present in vention arereconstituted about 10% more fluid is required; that is, about 5 partsof fluid per part of dehydrated potatoes. This is a distinct advantagefor our product because it means that a smaller amount of dehydratedpotatoes is required to prepare a given amount of mashed potatoes.

The practice of our invention is further illustrated by the followingexamples. In these experiments, Idaho Russet Burbank potatoes ofspecific gravity 1.075 to 1.085 were used; these being of lower solidscontent than are normally used in conventional processes for makingdehydrated cooked potatoes. In all these experiments the potatoes wereabrasion peeled, hand trimmed, sliced into /B-lIlCh thick slices andrinsed to remove free starch. Dificrent portions of the lot were thengiven various precooking treatments as shown below, after which theywere cooked in live steam at atmospheric pressure (212 F.) for 16minutes. They were then mashed, diluted with water to about 20% solidscontent and dehydrated on a double drum dried as described in our abovementioned copending applications. The dried flakes thus obtained werereconstituted by addition of 1% parts by weight of cold milk and 3%parts of boiling water to each part of potatoes. The resulting productswere submitted to a panel of taste experts for evaluation as mashedpotatoes with especial attention to texture (mealiness).

The first series of experiments was run to determine the optimumtemperature for the precooking step. In this series the sliced potatoeswere immersed for 30 minutes in water maintained at the specifiedtemperature. They were then cooked, dehydrated, reconstituted andevaluated as described above.

Table I.Efiect of temperature of precook Temp. of

Texture and Quality of Product Preeook, F.

Example Excessively mealy; grainy; slight off-flavor fair quality.Optimum mealmess; excellent quality. Less mealy than 2; more than 4;excellent quality. 1 Less mealy than 3; more than 5; good quality.Pasty; no mealiness; poor quality.

180 No precook.

Table II.--E1fect of time of precook Texture and Quality of ProductExample Time, Min.

Slightly pasty; fair quality, better than 5. Good meallness, nopastiness; good quality. Optimum mealiness; highest quality.

Very mealy; good quality.

I Some loss of flavor due to removal of soluble components.

In another series of experiments, the potatoes were precooked in steamrather than in water. The products thus obtained were in general similarto those precooked in the water bath, though most tasters rated themslightly less mealy than samples precooked in a water bath at the sametemperature and for the same time. Loss of flavor was less with thesteam precook, presumably because of the reduced leaching effect of theprecook treatment.

Experiments with high solids Idaho Russets or with high or low solidsMaine Russets, Katahdins or Kennebecs showed the same qualitativeeffects of time and temperature of precooking, although in general, thequality of the products from high solids potatoes was rated slightlyhigher than that from low solids potatoes. This difference, however, wasnot due to improvement in graininess since optimum graininess could beobtained from any type potatoes by proper choice of time and temperatureof precook.

In the above examples all the experiments involved drying the mashedpotatoes on double drum driers. This was done so as to enable directcomparison of the products precookcd at different temperatures or fordifierent times and should not be construed as indicating that otherprocesses and equipment for the dehydration step cannot be used. On thecontrary, all the conventional dehydration processes yield improvedproducts when the potatoes to be dehydrated are precooked according tothe present invention. Our process is particularly suited to theproduction of dehydrated potato dice, flakes and granules. In theproduction of dice, the cooking step is omitted and the precooked diceare sent directly to the drier.

We claim:

A process forproducing dehydrated potatoes comprising precooking rawpotatoes at a temperature of about to F. for about 10 to 60 minutes,cooking the precooked potatoes at about 212 F. for about 16 minutes,mashing the cooked potatoes, drying the mashed potatoes to a finalmoisture content of about 4 to 10% by applying a film substantially ofmonocellular thickness of the mashed potatoes to a heated surface, andrecovering the dried potatoes from said surface.

References Cited in the file of this patent UNITED STATES PATENTS2,190,063 Gano Feb. 13, 1940 2,339,757 Baer Jan. 25, 1944 2,439,119Willets et al. Apr. 6, 1948 2,564,296 Bostock Aug. 14, 1951 FOREIGNPATENTS 436,353 Great Britain Oct. 9, 1945

